1. Field of the Invention
The present invention relates to a clamp apparatus for clamping a workpiece with a clamp arm, which operates in accordance with the driving action of a driving unit.
2. Description of the Related Art
Conventionally, for example, in welding components of automobiles or the like, a clamp apparatus has been used for clamping the components (for example, see Japanese Laid-Open Patent Publication No. 9-192968).
In Japanese Laid-Open Patent Publication No. 9-192968, as shown in FIG. 10, a clamp apparatus comprises an outer cylinder 2 and clamp arms 3a and 3b. The outer cylinder 2 has a contact surface 1 at a top end for a workpiece (not shown) to be in contact with the contact surface 1. The clamp arms 3a and 3b clamp the workpiece on the contact surface 1. At one end of the outer cylinder 2, a positioning pin 4 is arranged being inserted into an unillustrated positioning hole defined in the workpiece.
At the other end of the outer cylinder 2, a driving cylinder 5 for a positioning pin and a driving cylinder 6 for clamp arms are respectively provided. The driving cylinder 5 for a positioning pin changes an external diameter of the positioning pin 4 with respect to the positioning hole by displacing the positioning pin 4 in an axial direction. The driving cylinder 6 for clamp arms displaces the clamp arms 3a and 3b in the axial direction.
The conventional clamp apparatus disclosed in Japanese Laid-Open Patent Publication No. 9-192968 requires two driving units, that is, the driving cylinder 5 for displacing the positioning pin 4 and the driving cylinder 6 for operating the clamp arms 3a and 3b. Therefore, in the above clamp apparatus, there are disadvantages that the size of the entire apparatus becomes large and production costs thereof become high. Further, when the above clamp apparatus is provided in an arm of a robot, there is a disadvantage that the arm of the robot suffers from a heavy load, since the size of the entire apparatus becomes large and the weight thereof becomes high.
A general object of the present invention is to provide a clamp apparatus for operating a positioning pin and a clamp arm respectively by one driving unit, thereby allowing the entire apparatus to have a compact shape and to have a light weight.
A main object of the present invention is to provide a clamp apparatus for operating a positioning pin and a clamp arm respectively by one driving unit, thereby reducing the production cost thereof.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.